1. Field of the Invention
Exemplary aspects of the present invention relate to a development device, an image forming apparatus, and a process cartridge, and more particularly, to a pre-mixed-type development device, and an image forming apparatus and a process cartridge incorporating the pre-mixed-type development device for supplying fresh carrier or developer to the development device.
2. Description of the Related Art
A related-art image forming apparatus, such as a copier, a facsimile machine, a printer, or a multifunction printer having at least one of copying, printing, scanning, and facsimile functions, includes a tandem-type image forming apparatus for forming a color toner image on a recording medium (e.g., a transfer sheet) based on image data scanned using electrophotography. Such image forming apparatus includes four image forming devices, in each of which a charger, a development device, and a cleaner surround an image carrier. Thus, for example, the chargers charge surfaces of the image carriers. An optical writer emits light beams onto the charged surfaces of the image carriers to form electrostatic latent images on the image carriers according to the image data. The development devices develop the electrostatic latent images with yellow, magenta, cyan, and black toners to form yellow, magenta, cyan, and black toner images on the image carriers, respectively. The toner images are transferred from the image carriers and superimposed onto an intermediate transfer belt. The superimposed toner images are then transferred onto a transfer sheet to form a color toner image on the transfer sheet. The cleaners clean the surfaces of the image carriers after the toner images are transferred from the image carriers onto the intermediate transfer belt. Finally, a fixing device applies heat and pressure to the transfer sheet bearing the color toner image to fix the color toner image on the transfer sheet, thus forming the final color toner image on the transfer sheet.
The development device may be a pre-mixed-type development device, in which fresh carrier particles (hereinafter “carrier”) are added as needed to a developer containing toner and carrier, and which is itself contained in the development device. Accordingly, used carrier is discharged from the development device when the fresh carrier is added, preventing deterioration of toner image quality caused by carrier deterioration over time.
In one example of such a pre-mixed-type development device, when an amount of a developer conveyed to a developer outlet exceeds a predetermined level due to supply of fresh carrier, surplus developer overflows the developer outlet and is conveyed through a discharge conveyance path toward an opening provided in a bottom of the discharge conveyance path, so that the surplus developer falls from the opening into a waste developer container.
However, the discharge conveyance path protrudes from a side of the development device, increasing the size of the development device in a short direction of the development device. Consequently, in order to install such development device in the tandem-type image forming apparatus, more space is needed between the adjacent image forming devices, increasing the size of the image forming apparatus as a result.
Further, the discharge conveyance path is provided near a bottom of the development device. Accordingly, the waste developer container is provided at a position substantially below that of the development device. Consequently, when the development device is installed in the tandem-type image forming apparatus, the image forming apparatus has an increased height to prevent the waste developer container from interfering with the intermediate transfer belt provided below the development device.
Obviously, such increased size of the development device is undesirable, and accordingly, there is a need for a technology to decrease the size of the pre-mixed-type development device.